1. Field of the Invention
The present disclosure relates to a vehicle headlamp capable of changing a light distribution pattern in accordance with the vehicle's operating condition.
2. Background
Generally, a vehicle headlamp of a projector type is arranged to form a light distribution pattern for a low beam having a cutoff line at an upper end edge by using a reflector to reflect light emitted from a light source of a halogen bulb or a discharge bulb and projecting reflected light to a front side by a projecting lens while blocking a portion of the reflected light by a shade.
Further, in recent years, a headlamp system, referred to as AFS (Adaptive Front Lighting System), has been proposed for producing a visual environment to facilitate safer driving by optimally controlling light in accordance with the vehicle's operating condition.
To move an entire lamp piece unit for a low beam of a vehicle headlamp in a left and right direction in cooperation with a steering angle or a vehicle speed, one AFS includes, for example, electronic control. As the vehicle travels around a curve, light is irradiated in a direction the vehicle turns, so that a wide field of view, including a steady gazing point viewed by a driver, is ensured to enable the driver quickly to recognize a hazard (e.g., a person, an object, an animal, a parked vehicle or the like) and to take evading action to maintain safety.
Further, recently there has been developed a light amount variable distribution type AFS for producing an optimum light distribution in accordance with various road conditions (e.g., suburb, motorway), weather conditions (e.g., rainy weather, fog), a vehicle speed or the like. In the future, it is expected to realize a further safe running environment by using such a light amount variable light distribution type AFS.
Japanese patent documents JP-U-05-072005 and JP-A-06-052702 propose vehicle headlamps for realizing a variable light distribution to change a light distribution pattern by moving a reflector fixedly provided with a light source bulb relative to a projecting lens.
However, according to the vehicle headlamp described in the foregoing references, although the position of a region having a large light amount in a light distribution pattern projected to the front side (i.e., a hot zone) can be changed, a change in the illuminance distribution cannot be obtained by partially increasing or reducing the illuminance. Therefore, the vehicle headlamp is not suitable for forming a light distribution pattern to obtain a light distribution of a motorway distribution capable of being used, for example, along a motorway or the like, or a wet light distribution capable of being used in rainy weather.